Apparatus for spray drying pulverulent materials



Dec. 3, 1963 w. T. DARNELL 3,113,062

APPARATUS FOR SPRAY DRYING PULVERULENT MATERIALS Filed Oct. 17, 1958AHHHHHH United States Patent 3,113,962 APPARATUS FOR SPRAY DRYHNGPULVERULENT MATERIALS Walter T. Darnell, 19A (lourt Drive, Wilmington 5,Del. Filed Get. 17, 1958, Ser. No. 767336 8 Claims, or. tea s Thisinvention relates to drying pulveru-lent materials and to apparatus andmethods thereof. More particularly, this invention relates to a methodfor creating an improved fiow of fluid drying medium and to apparatusfor effecting improved drying.

Hitherto, drying of pulverulent particles was accomplished by causingthe drying medium to flow in the drying chamber in a turbulent manner.The particles to be dried were injected into the turbulent dryingmedium, and one could not determine accurately the particle travel pathprecisely nor the retention time of a particle within the dryingchamber. Because different particles were retained in the drier fordifferent time lengths, uniform drying rate was not attained.Accordingly, certain particles were heated more, being consequentlydrier than other particles. Non-uniform drying, in many instances,affected the final product adversely, either injuring the product, asfor example, with food-stuffs or making it difficult to place theproduct in its original liquid form.

Accordingly, an object of this invention is the provision of methods fordistributing fluid flow through a chamber in a uniform fashion. Anotherobject is to minimize turbulence. Still another object is providingapparatus for producing substantially uniform straight line flow. Theseand other objects will appear hereinafter.

The objects of this invention are accomplished by passing the fluiddrying medium, usually a heated gas, through an inlet into the chamberinto which the material to be dried is being fed, the gas inlet beinglocated above the inlet for the material being dried and being locatednear a foraminous plate which extends vertically in the chamber. Thus,all or most of the incoming medium, is forced through the foraminousdistributor which is located away from the inlet at about 1 to about 2times the diameter of the inlet, and the medium is broken up intosmaller streams. That portion of the medium which does not go throughthe plate is forced downwardly, for the spray drier is usuallypositioned vertically, and this portion and the bulk of the mediumpassing through the foraminous distributor are forced through a secondforaminous plate which is located a short distance from the end of thefirst plate. This second plate extends transversely in the chamber. Allthe drying medium, whether it passes through the first plate, downwardlyto its lower end or under this end, is forced through the second plate,but with the distribution effected by the first plate the medium is fedin a substantially uniform manner to the second plate.

Thus, the apparatus of this invention comprises a material treatingchamber which has an inlet for the liquid, semi-solid or solid materialthat is to be dried, and inlet for the fluid drying medium, and a means,comprising at least two foraminous plates, for distributing the dryingmedium in substantially straight-line, uniform flow. While the chamberhas an outlet for the drying material and a collection means for thedried material, it is substantially enclosed and is usually in avertical position. The material dispensing means is usually positionedat the top in the center of the second baffle and generally has arotating atomizing disk. The top or inlet section of the chambercomprising the inlet and the foraminous plates provides a distributinghead and uniform straightline flow. By this invention the turbulence isminimized and all the materials passing through the chamber areuniformly distributed. The drying rate is uniform, for each particle ofthe wet material is subjected. to about the same amount of heat forabout the same period of time. The dried product has uniform dryness andother physical characteristics so that it may be reconverted to itsoriginal consistency with case.

This invention will be further understood by reference to thedescription and figures which follow, in which:

FIG. 1 is a side elevational partially in section of one form ofapparatus embodying the present invention; and

FIG. 2 is a transverse sectional view on line 22 of FIG. 1.

Referring to FIG. 1, reference numeral 10 designates generally a spraydryer comprising a cylindrical drying chamber 11 which terminates at itsdischarge end in a conical portion 12. to which a discharge duct 13 isconnected. The top of the chamber is closed by a flat top portion 14.The drying medium enters the chamber 11 through an inlet duct 15 whichextends radially with respect to the chamber adjacent the upper endthereof. The material to be dried maybe dispersed into the chamber byany conventional injecting or dispersing apparatus, preferably in such amanner that the particles of material being dried are disperseduniformly throughout a major portion of the upper end of the dryingchamber. As shown, a central cylinder 16, having a vertical axiscoincident with the vertical axis of the drying chamber, projectsdownwardly into the drying chamber 11 and supports a rotatable atomizingdisc 17 for dispersing the particles to be dried into the chamber. Thisdistributes the particles to be dried uniformly to the drying mediumstreams.

In accordance with the present invention, means are provided to causeuniform straight-line flow of the drying medium through the dryingchamber so that. at any cross section through the chamber, the flow ofdrying medium follows a straight line or is substantially straight andthe velocity of flow at each point across the section is substantiallythe same as the velocity at each other point across the section. Toaccomplish this, baffle means are mounted in the upper portion of thechamber so that the drying medium entering through the inlet duct 15 isdiffused to cause a substantially straight-line flow in the dryingchamber with a uniform fiow distribution at all points transversely ofthe chamber. In the illustrated embodiment of the present invention, atransverse bafile plate 18, one of at least two co-acting distributors,is carried by the chamber extending transversely of the upper end of thedrying chamber and usually in substantially parallel relationship withthe top plate 14 of said chamber. The transverse baffle plate 18 ispreferably located as shown in FIG. 1 intermediate the atomizing disc 17and the top plate 14 and is more preferably disposed therebetween adistance below the top plate proportional to a ratio of the inlet ductdiameter a; and the chamber diameter d In the actual embodiment thedistance the transverse baffle plate 18 is spaced from the top of thechamber, referred to has h is equal to approximately the chamberdiameter d plus /2 the inlet duct diameter (1,. As a further importantelement of this invention, a vertical baffle plate 19 is aflixed to thetop plate 14 and extends downwardly toward the transverse baffle plate18. The substantially vertical plate 19 is preferably mounted betweenthe dispensing means and the inlet duct 15 and is positioned to allow aclearance between the lower edge of said vertical bafile plate 19 andthe upper surface of the transverse baffle plate 18. In the illustratedembodiment, the baffle plate 19 protrudes downwardly from the top adistance b that may vary from a distance equal to the diameter of theinlet duct a, to /3 the chamber diameter d plus /2 the inlet ductdiameter d The clearance between the two plates or baflles may be fromabout A to about A of the drying chamber diameter, d

In the preferred embodiment as shown in FIG. 1, the lateral displacementa of the vertical bafiie plate 19 from the end of the inlet duct mayrange from one to two times the inlet duct diameter 41,. While it ispreferable to have the baffle plate 19 substantially vertical orsubstantially at right angles to the baffle plate 18, the baffle plate19 may also be positioned at a small angle, for example, up toapproximately 20, from the vertical, either toward or away from theinlet.

in addition to the proper positioning of the bafile plates in the topportion of the chamber to achieve thereby substantially uniformstraight-line flow of the drying medium through the chamber, an equallyimportant feature of the present invention is that the plates beprovided with openings 20, 20 therein to diffuse the drying mediumproperly. Preferably, the openings 29 comprise a plurality of grilledapertures extending through the plates, arranged to form a uniformpattern. More preferably, the openings 20 are arranged to extendtransversely of the bafile plates. The perforated, substantiallyvertical baffle plate 19 may have an open area in the order of from 23to 40% of the total area and the transverse baffie plate may have anopen area ranging from 12 to 40% of the total area. When, for examplethe value of the 'inlet duct diameter d, to the chamber diameter d wasone to eight and the perforated area in each plate was fixed at 23% ofthe entire area, a decrease of about 19% resulted in the overall powerrequirements, as compared to the power required to force the dryingmedium through the drying chamber with no baflle plates. Reduction inthe power needs can be attributed to the decreased dissipation of themomentum energy into eddy losses which results from a streamlining ofthe flow.

Although the general configuration of the drying chamber aside from thebattle plates is of the conventional type, in the present inventioncertain dimensional relationships are preferred to obtain the desiredstraight line flow characteristics. Therefore, in addition to certainpreferred dimensions of the baffles, corresponding preferred dimensionsare desirable in certain diameters and overall dimensions of the chamber11 and associated elements. For example, in the preferred embodiment,the inlet duct diameter d is approximately /8 to /3 of the chamberdiameter d and the height of the drying chamber h2 from the transversebafile plate 18 to the top portion of the conical section 12 is about 2to 3 times the chamber diameter d In operation, the drying medium,usually heated air, passes through the inlet duct into the inletchamber. Partial diffusion of some of the air is effected when it passesthrough the vertical baffle plate 19 while the remainder is diver-teddownwardly where the flow is divided. A portion of the downwardlydirected flow passes through the perforations 20, 26 in the transverseplate intermediate the inlet duct 15 and the vertical baffle 19. Theremaining portion passes through the opening formed by the lower edge ofthe vertical baffie 19 and the transverse baffle 18 and thence throughapertures in the transverse baflle. The combined diffusion results in auniform dispersion of the gaseous medium with a minimum of turbulenceover the entire cross section of the flow chamber. While additionalforaminous plates may be used, they are not usually needed, for thecooperating baflles of this invention co-act very effectively. The fluidmedium may be air, nitrogen, carbon dioxide, vaporized liquids and thelike, and these may be used at whatever temperature is desired. Mostfrequently heated air is used.

While the present invention has been illustrated and described inconjunction with spray drying apparatus, it will be apparent that theapparatus for producing uni form straight-line fiow through a chambermay be readily applied to equipment other than spray dryers. Forexample, this uniform straight-line flow may also be utilized in dryingchambers of conventional loop dryers, tray, or conveyor dryers, and mayalso be used in conjunction with spray cooling towers and dispersiondryers. The principles of this invention are applicable to a variety ofand independent of the means of atomization or material distribution.This invention may be applied also to tunnel dryers, humidificationtowers, gas absorption and gas absorption towers, gas heaters or heatexchangers and gaseous phase chemical reactors.

From the foregoing, it will be apparent that the present inventionprovides a novel improvement in dryers and the like wherein a dryingmedium or the like is diverted by a series of baffles in such a mannerto produce a straight-line flow of the medium through a chamber atuniform velocity regardless of the total flow of the medium. Thevelocity components are essentially axial, and with reference to theflow in the cylindrical coordinate systems embodied in most dryers theradial and tangential velocity components :are negligible. Thestraight-line flow was verified by anemometer measurements and by staticpressure measurements.

The process and apparatus of this invention are particularly important,advantageous and economical in applications in industry where headspaceis limited; that is, the height of the chamber available for gasdistribution is small, as, for example, only one-fifth of the chamberdiameter. Similarly, if the inlet is relatively small as compared to thechamber diameter, as, for example, as small as about one-eighth, thisbeing an inlet area ratio of this invention can and does provide aprocess and apparatus for getting substantial power savings and uniformresults.

From the above it can be seen that the principles of this inventionapply :to structures having dimensions reasonably equivalent to thosementioned. Thus, the distance h may be as much as /8 the chamberdiameter plus the diameter of the inlet at its discharge end. Theperforations in the plate may be about to about inch in diameter. Theseare usually circular and uniformly placed and :while other arrangementsmay be made, round openings uniform in place and size are preferred.Similarly, the distance b may be, depending upon the location of thetransverse plate, lengthened or shortened somewhat, the specifieddimensions being preferred.

While the invention has been disclosed herein in connection with certainembodiments and certain structural and procedural details, it is clearthat changes, modifications or equivalents can be used by those skilledin the art; accordingly, such changes within the principles of thisinvention are intended to be included within the scope of the claimsbelow.

I claim:

1. A distributing head for uniformly dispersing a drying medium used todry particles in a spray dryer or the like which head comprises asubstantially enclosed chamber; a cover plate enclosing the top portionof the chamber; an inlet duct at one end of said chamber andinterconnected with said chamber and providing a passageway for agaseous medium being forced into said chamber; a foraminous baffleplate, through which said medium passes, extending substantiallytransversely and across the cross-sectional area of the chamber in aspaced parallel relationship with the cover plate, said bafile platespaced downwardly from the cover plate a distance varying from about thechamber diameter plus about /2 the diameter of the inlet duct dischargeend to about the chamber diameter plus about the diameter of saiddischarge end; a second foraminous baflle plate within the chamber andprojecting substantially vertically downward from the cover plate towardsaid transverse baflie plate a distance varying between a distance aboutequal to the dimension of the diameter of the inlet duct discharge endto a distance about equal to /3 the chamber diameter plus /2 the saiddischarge end diameter, said second plate being spaced from the inletduct discharge end a distance ranging from about one to about two timesthe said discharge end diameter; and means for applying pressure to saidmedium, said pressure and said bathe plates being diffusers for saidmedium and causing uniform flow of said medium.

2. A distributing head for uniformly dispersing a drying medium used todry particles in a spray dryer or the like which head comprises asubstantially enclosed, elongated drying chamber; at one end of saidchamber an inlet for said particles; at the same end of said chamber aninlet duct interconnected with said chamber through which a dryingmedium may be forced into said chamber; a foraminous bathe plateextending substantially transversely and across the cross-sectional areaof said chamber; a second foraminous bathe plate mounted in the chambersubstantially perpendicular to said first bathe plate and located in thepath of a drying medium forced into the chamber, said bathe platesoperable to diffuse the drying medium and to cause uniform how of themedium through the chamber by means of a plurality of uniformly spacedopenings in said bathe plates through which the drying medium passes,said openings in the first bathe plate defining an open area within therange of approximately 12% to about 40% of its total surface area andsaid openings in the second bafile plate defining an open areacomprising between about 23% and about 40% of its total surface area;and means to remove the dried particles from said chamber.

3. A distributing head for uniformly dispersing a drying medium used todry particles in a spray dryer or the like having therein means todistribute uniformly the particles to be dried and having means toremove the resultant dried particles and said medium which headcomprises a substantially enclosed drying chamber mounted with its longaxis in the vertical position; an inlet duct at one end of said chamberand interconnected with said chamber through which a drying medium maybe forced into said chamber; a foraminous baffle located near said inletduct and positioned parallel to the long axis of the said chamber; and asecond foraminous bathe positioned near the free end of said firstbaflle and positioned transversely of said chamber to run from one wallof said chamber across to the other wall and providing a clearancebetween it and the said free end of the said first bathe, the saidbathes coacting to diffuse said drying medium prior to the meeting ofsaid medium with the said particles distributed to be dried.

4. A spray dryer or the like comprising a substantially enclosedchamber; a cover plate enclosing the top portion of the chamber; aninlet duct at one end of said chamber and interconnected with saidchamber through which a drying medium may be forced into said chamber;dispensing means disposed in said chamber operable to discharge materialto -be dried into the chamber; a foraminous bathe plate extendingsubstantially transversely and across the cross-sectional area of thechamber in a spaced, parallel relationship with the cover plate, saidbafile plate being spaced downwardly from the cover plate a distancevarying from about the chamber diameter plus about /2 the inlet ductdiameter at its discharge end to about the chamber diameter plus theinlet duct discharge diameter; a second foraminous bathe plate withinthe chamber and projecting substantially vertically downward from thecover plate toward said first baflle plate a distance varying between adistance equal to about the dimension of the said inlet duct diameter toa distance equal to about /a the chamber diameter plus about /2 the saidinlet duct diameter, said second plate being spaced from the inlet ductentrance a distance ranging from about one to about two times the saidinlet duct diameter; means to apply pressure on said drying medium toforce it through said chamber, said pressure and said bathe platesoperable to diffuse the drying medium and to cause uniform how of themedium through the chamber; and means to remove the dried particles andsaid drying medium from the drying chamber.

5. Apparatus comprising a generally cylindrical material treatingchamber; a cover plate enclosing the top portion of the chamber; aninlet duct adjacent the cover plate and interconnected with said chamberbeing located at one end of said chamber and providing a passageway fora gaseous medium being forced into said chamber; dispensing means,disposed concentrically and extending downwardly in said chamber, todischarge material to be treated into the chamber; a foraminous batheplate extending substantially transversely and across thecross-sectional area of the chamber positioned between the cover plateand the discharge end of said dispensing means; and a second foraminousbathe mounted in the chamber substantially perpendicular to saidtransverse bathe plate and located in the path of said medium andbetween the discharge end of said inlet duct and the dispensing meansbut terminating just above the said transverse bathe plate, said batheplates being diffusion agents for said gaseous fluid medium and causinguniform how of said medium.

6. A spray dryer or the like comprising a substantially enclosed dryingchamber; an inlet duct at one end of said chamber and interconnectedwith said chamber through which a drying medium may be forced into saidchamber; dispensing means disposed in said chamber operable to dischargematerial to be dried into the chamber; a foraminous bathe plateextending horizontally and substantially transversely and across thecross-sectional area of the chamber; a second foraminous bathe platemounted in the chamber substantially perpendicular to said first batheplate and positioned near the said inlet duct and in the path of thedrying medium forced into the chamber, but terminating just above thefirst bafile plate; pressure means for forcing said medium through saidchamber, said pressure means and said bathe plates co-acting to diffusethe drying medium and cause uniform how of the medium prior to themediums reaching the said discharged material; an outlet for saidmedium; and means to remove the dried particles from the drying chamber.

7. A distributing head for uniformly dispersing a drying medium used todry particles in a spray dryer or the like having therein means todistribute uniformly the particles to be dried and having a means toremove the resultant dried particles and said medium which headcomprises a substantially enclosed drying chamber; an inlet ductinterconnected with said chamber through which a drying medium may beforced into said chamber; means including a pair of bathe plates, oneextending substantially transversely and across the cross-sectional areaof said chamber and the other being substantially at right angles tothis transverse plate and located near the orifice of said inlet ductwhich orifice is within said chamber, the said pair coacting to diffusethe drying medium forced into the chamber and to cause uniform how ofthe medium through the chamber; and means defining a plural ity ofuniformly spaced openings extending transversely of said plates throughwhich the drying medium passes, said openings having a diameterdimension that varies between about and about inch.

8. Apparatus for causing substantially straight-line how of a gaseousmedium through an elongated, vertical chamber comprising the saidchamber; at the upper end an inlet duct for connection with said chamberand providing passageway for said medium into said said chamber; nearsaid end a foraminous member extending substantially transversely andacross the cross-sectional area of said chamber; a second foraminousmember located intermediate said inlet duct and said transverseforaminous member near said inlet duct, said second foraminous memberbeing located at a distance from said inlet duct of approximately one toabout two times the inlet diameter at its discharge end and extendingdownwardly into said chamber from the top thereof across and spaced fromsaid inlet and being substantially perpendicular to said transverseforaminous member and spaced therefrom to provide a clearancetherebetween; and at the other end of said chamber an outlet for saidmedium.

References Cited in the file of this patent UNITED STATES PATENTS1,782,822 Hechen-bleikner Nov. 25, 1930 8 Voorhies Aug. 30, 1932Lutenbacher Oct. 23, 1934 Short June 20, 1939 Kuhl Jan. 25, 1944 HarmsFeb. 26, 1952 FOREIGN PATENTS France Jan. 10, 1944 UNITED STATES PATENTOFFICE CERTIFICATE OF CORRECTION Patent No. 3,113,062 December 3, 1963Walter T. Darnell It is hereby certified that error appears in the abovenumbered patent requiring correction and that the said Letters Patentshould read as corrected below.

In the grant, lines 1 to 3, for "Walter T, Darnell, of Wilmington,Delaware," read Walter T. Darnell, of Wilmington, Delaware, assignor toFundamental Research, Inc. a corporation of Delaware, line 12, for"Walter T. Darnell, his heirs" read Fundamental Research, Inc, itssuccessors in the heading to the printed specification, line 4, for"Walter T. Darnell, 19A Court Drive, Wilmington 5, Del." read Walter T.Darnell, Wilmington, De1.,, assignor to Fundamental Research, Inc, acorporation of Delaware column 1, line 9, for "thereof" read thereforline 11, after "of" insert the column 6, line 67, strike out "said",third occurrence.

Signed and sealed this 26th day of May 1964,

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J BRENNER Attesting Officer Commissioner ofPatents

4. A SPRAY DRYER OR THE LIKE COMPRISING A SUBSTANTIALLY ENCLOSEDCHAMBER; A COVER PLATE ENCLOSING THE TOP PORTION OF THE CHAMBER; ANINLET DUCT AT ONE END OF SAID CHAMBER AND INTERCONNECTED WITH SAIDCHAMBER THROUGH WHICH A DRYING MEDIUM MAY BE FORCED INTO SAID CHAMBER;DISPENSING MEANS DISPOSED IN SAID CHAMBER OPERABLE TO DISCHARGE MATERIALTO BE DRIED INTO THE CHAMBER; A FORAMINOUS BAFFLE PLATE EXTENDINGSUBSTANTIALLY TRANSVERSELY AND ACROSS THE CROSS-SECTIONAL AREA OF THECHAMBER IN A SPACED, PARALLEL RELATIONSHIP WITH THE COVER PLATE, SAIDBAFFLE PLATE BEING SPACED DOWNWARDLY FROM THE COVER PLATE A DISTANCEVARYING FROM ABOUT 3/8 THE CHAMBER DIAMETER PLUS ABOUT 1/2 THE INLETDUCT DIAMETER AT ITS DISCHARGE END TO ABOUT 3/8 THE CHAMBER DIAMETERPLUS THE INLET DUCT DISCHARGE DIAMETER; A SECOND FORAMINOUS BAFFLE PLATEWITHIN THE CHAMBER AND PROJECTING SUBSTANTIALLY VERTICALLY DOWNWARD FROMTHE COVER PLATE TOWARD SAID FIRST BAFFLE PLATE A DISTANCE VARYINGBETWEEN A DISTANCE EQUAL TO ABOUT THE DIMENSION OF THE SAID INLET DUCTDIAMETER TO A DISTANCE EQUAL TO ABOUT 1/3 THE CHAMBER DIAMETER PLUSABOUT 1/2 THE SAID INLET DUCT DIAMETER, SAID SECOND PLATE BEING SPACEDFROM THE INLET DUCT ENTRANCE A DISTANCE RANGING FROM ABOUT ONE TO ABOUTTWO TIMES THE SAID INLET DUCT DIAMETER; MEANS TO APPLY PRESSURE ON SAIDDRYING MEDIUM TO FORCE IT THROUGH SAID CHAMBER, SAID PRESSURE AND SAIDBAFFLE PLATES OPERABLE TO DIFFUSE THE DRYING MEDIUM AND TO CAUSE UNIFORMFLOW OF THE MEDIUM THROUGH THE CHAMBER; AND MEANS TO REMOVE THE DRIEDPARTICLES AND SAID DRYING MEDIUM FROM THE DRYING CHAMBER.